I ordered a medium, which by the sizing chart should have fit. Taking into consideration that this type of garment is "form fitting," this shirt was too small. I could barely get the shirt on over my head, and once on, it fits very tightly around the neck. Very uncomfortable to me. Rather than send it back, my wife is going to keep it and try it herself. We'll see how that works out. I am not planning on ordering a size up. Instead, for about the same price I bought an Underarmour shirt of the same sort which has a decent size opening at the neck.